Association of serum beta-hCG levels with myosalpingeal invasion and viable trophoblast mass in tubal pregnancy

Abstract

Objective: To test the hypothesis that myosalpingeal invasion and viable trophoblast mass are associated with serum beta-hCG levels in tubal-ampullary pregnancy.

Methods: Twenty-seven salpingectomy specimens of tubal-ampullary pregnancies were assessed for the presence or absence of myosalpingeal invasion. The mass of viable trophoblast was quantified in terms of the number of high-power fields (x400) occupied. The cases were stratified into three groups: small, less than one field; medium, one or two fields; and large, more than two fields and/or embryo present. Beta-hCG was measured before the procedure (mIU/mL, Third International Standard).

Results: The mean (+/- standard error of the mean) beta-hCG level for the nine cases exhibiting myosalpingeal invasion was significantly higher than for the 18 cases without invasion (13,665 +/- 2986 versus 2169 +/- 870 mIU/mL; P = .0001). Beta-hCG levels greater than or equal to 5400 mIU/mL predicted myosalpingeal invasion in eight of nine cases (positive predictive value 89%). In contrast, levels less than 5400 mIU/mL were associated with lack of myosalpingeal invasion in 17 of 18 cases (negative predictive value 94%). The volume of trophoblast mass correlated with both beta-hCG levels (r = 0.647, P = .0003) and myosalpingeal invasion (r = 0.735, P = .0001). There was no invasion in the 13 cases in the group with small trophoblast mass, whereas two of five cases in the medium-mass group displayed myosalpingeal invasion. In this group, the mean beta-hCG for cases with myosalpingeal invasion was higher than in the cases without invasion (16,917 +/- 117 versus 3799 +/- 1094 mIU/mL; P = .003). In the group with large trophoblast mass, seven of nine specimens showed myosalpingeal invasion.

Conclusion: Both myosalpingeal invasion and viable trophoblast mass correlate positively with serum levels of beta-hCG. Myosalpingeal invasion is highly likely when beta-hCG levels reach 5400 mIU/mL.